Today, when farmers harvest their crop, they remove some crucial nutrients from the soil. Fertilisers replace many of these nutrients, and also increase the amount of certain chemicals such as nitrogen and phosphate. This allows the plants to grow more healthily. There are too types of fertiliser, organic and inorganic. Out of these two, organic is most frequently used because it is relatively cheap to purchase and very easy to apply. Inorganic fertilisers are highly soluble which allow the plants to easily take it up. However because this fertiliser is so highly soluble it can be readily leached into the waterways surrounding the fields. This can eventually lead to a process known as eutrophication. When these chemicals leak into rivers and lakes they fertilise algae and allow bacteria to grow. When these organisms die, they decompose and allow microbes to feed on them, this allows them to multiply. The effect is that the microbes use up all the oxygen causing many fish and other fresh water animals to die. This death produces more decomposition and thus produces even more microbes. For this reason, it is constant cycle declining the levels of oxygen in the lake or river. .
Nitrogen, a chemical which can leak into lakes and rivers is also a large problem. High quantities of this chemical in our drinking water has be known to cause "blue baby syndrome". This process prevents the haemoglobin from carrying enough oxygen, and results in a failure to respire. .
The increase in population in many global communities has meant an increase in the demand for food. Without fertilisers many farmers are not capable of producing crops and similar foods in large enough quantities and at a good enough quality. Because the use of fertilisers has been so heavy in the past, the use of fertilisers has become an essential that it seems we on global basis cannot live without. The demand for agriculturally produced food is very high and the competition among farmers to stay in business is tough.